Seekins doesn’t make GAPs rifles, they make the receivers and hand guards GAP uses to GAP’s spec. Different barrel, different trigger, different assembly, different QC, and a lot of different small parts.
I love Seekins, honestly just a great company with a quality product.... BUT!!
If you can snag a SP-10 with the updated gas system under $2,500 it's a good deal but if you're able to build I'd personally go with the Seekins builder kit and a Compass Lake or Craddock Barrel headspaced to a JP Bolt.
So basically the 6.5CM Hates!! a rifle length Gas system on any barrel shorter than 18" and it just beats the shit out of the brass and is prone to showing false pressure signs on the case heads, it really needs a shorter dwell time and that's what a longer Gas System provides. Proof was the first to figure it out with the design of their CamGas system.